Abstract: A whole volume quadrature coil is provided which has one side and two ends thereof open for easy patient access. The coil is comprised entirely of figure eight shaped coils.

Abstract: An NMR pulse sequence technique for use in the borehole environment is provided which uses CPMG pulses according to?W.sub.i -90-(t.sub.cp -180-t.sub.cp -echo).sub.j !.sub.iwhere j is the index of the CPMG echoes gathered, i is the index of the wait times in the pulse sequence, W.sub.i are the varying wait times before the CPMG pulses, and tcp is the Carr-Purcell spacing. Measurements are made of the signals induced in the formation as a result of the magnetic fields to find the spin-echo relaxation time T1. Using T1, the gas effect on formation parameters may be derived. Also, gas saturation and gas chemical composition can be derived. In addition, the diffusion coefficient of gas under reservoir conditions can be more than ten times larger than that of water, making the T.sub.2 relaxation time of gas more sensitive to static magnetic field gradients. In formations where gas occupies pores larger than about 10 .mu.m, this T.sub.2 effect (effect of diffusion on the measured T.sub.

Abstract: The apparatus including a mainly cylindrical RF coil (9) having a central axis (33) which extends in its longitudinal direction, which coil has a number of axial conductor elements (35) which extend parallel to the central axis across a mainly cylindrical surface, and end conductor elements (37) which extend around the central axis near the ends of the axial conductor elements. The axial conductor elements (35) extend pair-wise diametrically relative to the central axis and the RF coil (9) is arranged to generate a substantially cosinusoidal current distribution as a function of the position of the axial conductor elements on the circumference of the cylinder in order to enable generation and/or reception of a substantially uniform RF magnetic field which is oriented perpendicularly to the cylinder axis. Each of the end conductor elements (37) consists of a number of loop conductor segments (39) which corresponds to the number of pairs of axial conductor elements (35).

Abstract: A double-resonance coil for use in MRI having a coil element, a first input/output terminal coupled to the coil element, and a second input/output terminal coupled to the coil element. A first resonance means is coupled between the coil element and the first input/output terminal to cause the MRI coil to resonate at a first MRI frequency, and a second resonance means is coupled between the coil element and the second input/output terminal to cause the MRI coil to resonate at a second MRI frequency substantially different than the first MRI frequency. The double resonance coil includes a first frequency-blocking means coupled to the coil element for substantially preventing the second MRI frequency from being detected at the first input/output terminal and a second frequency-blocking means coupled to the coil element for substantially preventing the first MRI frequency from being detected at the second input/output terminal.

Abstract: A displacement sensor senses relative displacement between first and second members and includes a housing mounted to the first member. Magnet means having first and second pole tips is mounted to the housing. A flux sensor is mounted to the housing between the first and second pole tips. A target is mounted to the second member to form a flux path between the first and second pole tips having a reluctance that varies with displacement between the first and second members. The arrangement forms a first lossy flux path of fixed reluctance through the flux sensor and a primary flux path through the target. In one form the target has a surface configured to provide a gap height that varies with displacement. In another form the target has a surface configured to provide a target width that varies with displacement. The sensor may be used differentially by arranging two such sensors.

Abstract: For measuring magnetic properties of sheet material the sheet material is guided past a magnetic measuring system at a measuring distance defined between the sheet material and the magnetic measuring system. The sheet material is transported with a transport medium disposed between the measuring system and the sheet material. The measuring distance is determined substantially by the thickness of the transport medium. The thickness of the transport medium is selected to be smaller than a predetermined local resolution. If the local resolution is high enough it is also possible to detect magnetic printed images.

Abstract: A preprogrammed controller, preferably a stored program computer such as an IBM PC computer, is programmed to automatically control all the steps in the testing of a MR reproduce head. First, the magnitude of the sense current is established by command of the controller, and a voltage proportional to the sense current flowing in the head is monitored by the controller. An electromagnet, having high permeability pole pieces, and whose current is programmed by the controller provides a the magnetic field for exciting the MR head. The MR device is placed on an measured magnetic equipotential of the field of the electromagnet, and a Hall sensor magnetic detector is placed on the same magnetic equipotential line but in a different physical position from the MR device. The output of the Hall sensor is fed into the preamplifier electronics, digitized by a converter and this digital output is stored in the controller memory for future processing.

Abstract: An amplification device is provided for driving a gradient coil in an MR system, wherein the gradient coil is required to generate a rapidly changing gradient magnetic field during a first time period, and a substantially constant field during an immediately following second time period. The device includes a adjustable bus, for providing first and second voltage levels, and a switching or PWM amplifier. A switch is coupled between the bus and the switching amplifier for applying the first voltage to the amplifier during the first time period, and the second voltage to the amplifier during the second time period. The switching amplifier comprises an inverter for generating a PWM voltage in response to its input, and an LC filter for converting the PWM wave into a DC voltage. The switching amplifier generates a substantially higher coil driving voltage during the first period, in response to the first voltage level, than during the second period in response to the second voltage level.

Abstract: A displacement detector to obtain high-precision displacement detection with a small-sized, low-cost apparatus. A displacement detector comprises rectangular teeth formed on the outer circumference surface at a pitch of .lambda., a gearwheel made of a magnetic material, a magnet having a width larger than the pitch .lambda. of the gearwheel and so disposed that the N-pole thereof faces the teeth, and a pair of MREs constructed by alternately connecting the long strip portions and short strip portions thereof to have a zigzag shape. A uniform cyclic magnet field from the magnet to the gearwheel is formed within a gap between the gearwheel and the magnet. On the same phase of the magnet field are disposed the pair of MREs so that the directions of the long strip portions thereof and the directions of the magnetic force lines make angles of approximately 45.degree. and approximately 135.degree., respectively.

Abstract: Methods and apparatus for measuring pollutants contaminating earth formation. Specifically, the invention involves the three dimensional, spatially continuous imaging of sub surface conditions using electromagnetic induction techniques. The technique utilizes the resistivity of near surface volumes of earth formation in order to determine and graphically represent the magnitude and migration of pollutants. Included in the invention are the logging techniques and apparatus as well as the method of converting the captured data into a pseudo resistivity log suitable for a three dimensional imaging of sub surface conditions.

Abstract: A nuclear magnetic resonance imaging scheme suitable for three dimensional physiological function imaging such as brain function imaging. In this scheme, the pulse sequence is controlled to realize a three dimensional imaging sequence with a division scan in at least one of a first encoding direction and a second encoding direction. In other words, the pulse sequence is controlled to realize a three dimensional imaging sequence with first encoding gradient field pulses and second encoding gradient field pulses for defining regular sampling pitches in first and second encoding directions, where at least one of the first encoding gradient field pulses and the second encoding gradient field pulses has a lead-in pulse in regularly changing magnitude for each spin excitation.

Abstract: A system comprising a portable apparatus and employing a method of admittance versus frequency analysis to detect the existence of a fault in a de-energized electrical line regardless of whether the line contains branches. The portable apparatus comprises a capacitor unit detachably connected to a de-energized line, ground or a neutral conductor, a switch unit detachably connected to a de-energized line, the de-energized line being tested, and an insulated cable connecting the capacitor unit to the switch unit. The switch unit comprises a discharge switch that can be activated by pulling on the hot line tool. The capacitor unit comprises a capacitor which is discharged into the electrical line via the insulated cable and the switch unit when the discharge switch is activated to create a pulse.

Abstract: A magnetic imager 10 includes a generator 18 for practicing a method of applying a background magnetic field over a concealed object, with the object being effective to locally perturb the background field. The imager 10 also includes a sensor 20 for measuring perturbations of the background field to detect the object. In one embodiment, the background field is applied quasi-statically. And, the magnitude or rate of change of the perturbations may be measured for determining location, size, and/or condition of the object.

Abstract: The invention relates to a remotely accessible electrical fault detection system. According to one preferred embodiment, the system includes a weather-resistant housing having a mount adapted for mating to an aperture in an outer wall of a utility cabinet containing an electrical network; a circuit adapted for connection to the electrical network, wherein the circuit includes at least one of a transmitter and a receiver; and an antenna located inside the weather-resistant housing and coupled to the circuit. In operation, the transmitter can broadcast a radio frequency fault signal to a remote communication device, in response to the electrical network detecting a fault condition.

Abstract: A Josephson signal detector is presented which includes (1) a sensor with at least one Josephson junction (e.g., a SQUID) and (2) a comparator (e.g., an analog-to-digital converter); a measurement system using such detector; and a method of using such detector and measurement system. The detector can be, e.g., a digital SQUID. The detector can also include a readout circuit for reading out the output of the comparator. In one aspect of the invention, the sensor, or both the sensor and readout circuit, are powered by a DC current source. Through use of the DC current source, it is possible to provide, e.g., a digital SQUID, having reduced crosstalk and reduced fluctuation of ground potential, and which is kept from an increase in noise or a miss operation.

Abstract: Apparatus and method for monitoring a fluid reservoir traversed by at least one well comprising the placing of at least one electrode communicating to the surface and fixed in permanent manner in the well. Hydraulically isolating the section of the well in which it is located from the rest of the well and providing electrical coupling between the electrode and the reservoir. Subsequently, a current is passed through the reservoir; and an electrical parameter is measured, whereby a characteristic representative of the reservoir can be deduced.

Abstract: A method and apparatus for exciting a three-phase variable reluctance motor is used, for example, as an encoder system to commutate a rotor. The system includes a power source, a position sensor and excitation electronics. The position sensor is adapted to generate a plurality of variable induction values corresponding to relative motor torque rankings and absolute angular positions of the rotor. Excitation electronics is provided electric communication with the inductive sensor and the power source and is adapted to generate digital values of the inductance values corresponding to the motor torque rankings. Excitation electronics includes steering logic responsive to the digital values to generate an output signal having a value corresponding to the phase of the motor to apply current to so as to commutate the rotor.

Abstract: An electrical test device for testing the function of a receptacle ground fault circuit interrupter. The tester plugs into a receptacle and includes a current source, timer, testing circuit, and display. The current source introduces a substantially constant fault current between the hot and ground leads of the receptacle. Once this occurs, the timer begins counting time and generates a time count signal. The test circuit receives the time count signal and determines whether the interrupter enters a tripped state within a designated time. The testing circuit responsively generates a trip indicator signal reflecting whether or not the ground fault interrupter circuit tripped within the designated trip time. The display means receives the trip indicator signal and responsively indicates whether the interrupter functioned properly by tripping the designated trip time.

Abstract: In measuring a stress of a soft magnetic metal wire, an A.C. magnetic field exceeding a coercive force of the metal wire is applied to the soft magnetic metal wire with a tensile load applied thereto, using an exciting coil, thereby inducing an A.C. electromotive force through a detecting coil. An effective value of one or more higher harmonic wave components including a stress information of the soft magnetic metal wire in the waveform of the A.C. electromotive force is determined as a measurement amount. By taking higher harmonic wave components as an amount in this manner, the stress of the soft magnetic metal wire 4 can be measured correctly.

Abstract: A magnetic detection device including a biasing magnet for generating a bias magnetic field directed to an object of detection having a magnetic material; a magnetoresistance effective element disposed at an inclination of about 45.degree. to the direction of the bias magnetic field to provide a change in resistance caused by the bias magnetic field in accordance with movement of the object of detection, so as to detect a change in state of the bias magnetic field via the change in resistance of the magnetoresistance effective element; and the biasing magnet having a hollow portion containing a holder for holding the magnetoresistance effective element in a position between a surface of the biasing magnet and the object of detection and close to the surface of the biasing element.